Canoe to tri?

After considerable thought and reading on this board and an unfortunate incident this morning out fishing Im considering building something suitable from the keel up.

The freeboard on the canoe is just not enough to keep me dry in recent weather and altho I have stiffened the bottom and the sides where the spars connect the ama-- Im starting to see the hull flex in places where it didnt before. To prevent this from happening I would have to possibly rib the full length of the canoe...which would change the character of the canoe. In short, Im trying to do something the canoe was never meant to do.

Ive found a video of what I was trying to accomplish with the canoe -- but its not a canoe...

http://www.youtube.com/watch?v=UuhYlo1ImfY

I would modify this design a bit to allow for more standing deckspace and I think the amas could use a bit more rocker in the front but I think this would work well.

Thoughts?

 

This thing sure is dragging the transoms. Don't put rocker in front, put it in back, or make the amas longer and thinner at the back, if you want deck space for fishing, put it on top of the akas, so you are standing outside the main hull. You probably would go faster with a "speed" prop, if such a thing is available. How much does it weight?

 

Obviously, this thing was designed to plane. Hence the 14 kts.

Just not sure a more conventional design, such as a semi-dory, planing john boat, or plain, off the shelf, tin skiff wont get the same performance with the same hp.

The tri is cool looking and probably more stable. But fishing off it, or even rowing or paddling it around, should the engine conk out, may be a bit of a challenge compared to a more conventional design.

A non-planing version would probably have to be completely different to work well.

 

I like the layout-- but, yes the ama's need to be longer--extending past the transom by a few feet.

To me, the boat looks too ....."stiff" and I would want more curvy lines.

If the ama's were pointed aft instead of squared off how would that change characteristics?

I would want a deck that extended from center hull to ama's --maybe even behind the engine with room enough to tip the engine up.

 

The 'stiff' lines make it plane better.

That is also why the ammas extend aft the main hull transom. To keep the stern from squatting.

If that's what you are after, why not buy the guy's plans?

If you are after a non planing boat, the majority of the weight, you, have to be further forward. This is so the stern can have some decently gentle curves in it to let the water slip by.

The engine can then be lighter and have much less power.

The ammas should be lengthened and moved further forward and their shape should have gentle curves in the stern.

You may end up going one half to two thirds the speed of the planing version, but use much less fuel per mile doing so.

Boats don't have the shape they do to look pretty. They have that shape because it works best for their designed purpose.

 

With all due respect about the planing discussion, watch the video and look at the huge stern wave. That thing is a dog. If we saw a video at higher speed I might change my viewpoint. Can it actually go faster?

 

Maybe I like graceful lines a bit better and would definately give the amas more of a rocker on front as well as more rounded on bottom. The main hull needs to be suited to a purpose but shouldnt the bow have a more gradual angle for easier planing and wave breaking?

The extension of the ama's past the main (aka?) hull transom makes sense.

 

The problem with a rockered surface ( rounded vertically fore and aft) is that it doesn't provide a flat surface, or cuts down on the amount such available. The portion of the rocker in the stern is even worse, with with the water following the curve up, instead instead of breaking free.

The amas being aft of the main hull do no good at all, unless the boat is improperly loaded to begin with, or intended for mostly planing. The amas on a trimaran should not be supporting any of the boat's weight in the case of a non-planing boat.

The big decision here is if you want a planing hull.

A trimaran, or any boat with a very narrow waterline, can usually easily exceed normal displacement speed by quite a margin, making planing unnecessary for reasonable speeds.

 

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What a neat little boat-thanks for posting it!

 

In the early 1960's I rented a small fiberglass powerboat for a day trip. Despite the small outboard (15 HP?) it planed easily, was a blast to use and even at speed had remarkably little wash - although I still obeyed the speed limits!

I suppose these days we might call it a tunnel hull; in essence it was a cat with a full-length bridge which created a sort of console in the cockpit. That's all I can recall - I wasn't a boat person back then - but it struck me as a sensible and efficient design. Hope that helps . . .

 

I notice there are no comments about the video. There was a huge stern wave a very short distance behind the transoms. Unless this was taken before the transition to planeing, the flat hulls were not working well at all. It looks like not enough width to get to a plane combined with too much weight aft.

Theory's fine, opinions about appearance are individual desires, but how about a discussion about what we actually see?